Mini Composting

More mini composting means less garbage for cities.

Mini composting containers are used nationwide in classrooms, on balconies and tiny back porches, under kitchen sinks and in employee lounges. Every little bit counts toward improving the environment when averting recyclable garbage from landfills. Mini composting turns organic waste -- such as kitchen scraps and shredded paper -- into a loamy soil enrichment for houseplants as well as school, community and container gardens. The process demonstrates "hot" and "cold" composting and encourages urban gardening.

Hot Mini Composting

Hot composting usually is done outdoors in bins of varying sizes. It involves mixing "green" or nitrogen-rich materials, such as kitchen scraps, with carbon-rich "brown" materials, including paper and dry leaves. These materials usually are layered in a pit in the ground or in a large, ventilated bin. Periodically moistening and turning the layers helps the materials to mix, heat up and decompose with the help of beneficial insects and bacteria. (See Resources 1) Mini hot composting containers range from bottles and jars for school experiments to barrel-shaped tumblers tucked away on balconies and back porches.

Cold Mini Composting

Vermicomposting -- composting with the help of red wriggler earthworms (Eisenia fetida) -- is one of the most prevalent forms of mini composting for city dwellers. Red wrigglers can't take heat and don't dive deep into compost, which is why they aren't used in hot heaps. Vermicomposting bins should be opaque and can be as small as a 16-quart, plastic storage bin that is lidded and ventilated. They should contain damp but not soggy biodegradable bedding, such as shredded newspaper, along with kitchen scraps and other organic munchies including old wool or cotton socks. The worms digest the materials, leaving behind nitrogen-rich waste called castings. Their tunneling action also helps rot the bin materials. (See References 1 and 2; Resources 3 and 4) Other, much slower, cold composting methods are done outdoors and involve piles of organic matter that are aerated but not turned.

Classroom Projects

One thing to remember when involving students in hands-on lessons about composting is that decomposition is time consuming, whether occurring outdoors in hot bins or indoors through worm bins. The process usually takes at least two months from the time the bin is full until all the material breaks down. It is a good unit to begin in the autumn. One way to make the process more engaging is to let each student create a mini-hot bin in a clear container -- such as a quart, wide-mouth canning jar with netting over the opening -- to make observation and facilitate mixing. These containers can be grouped under black plastic in a sunny location indoors or outside. (See References 3; Resources 5) On a more sophisticated level, Cornell University offers an online booklet, "Composting in the Classroom: Scientific Inquiry for High School Students," that includes mini composters constructed from soda bottles. (See References 4)

Urban and Office Composting

Urban balconies and back stoops are good locations for small compost containers including barrel-shaped tumblers that mix compost ingredients when rotated by hand. (See Resources 2) Toronto gardener Marco Pagliarulo hides a tiny tub of compost on his balcony by nesting it in a larger planter. He fills the space between the outer wall of the compost tub and the inner wall of the planter with potting soil and grows plants in that narrow ring. (See References 5) Another way to mini compost is to collect food trash at offices and deliver it to large composting centers. The Portland city government encourages office workers to gather compostable materials and deliver them to the municipal composting center. (See References 6) A pilot project involving mini compost collection receptacles in Harvard University offices has spread throughout the campus, which now collects about 4,000 tons of compostables annually. (See References 7)

About the Author

Alicia Rudnicki's Library Mix website blends book buzz for all ages. A gardener, she writes for California's Flowers by the Sea nursery. She has a Bachelor of Arts in journalism from UC Berkeley, a Master of Arts in education from CU Denver, and has taught K-12.